1. Technical Field
The present invention relates to a steering wheel including a heating element, and more particularly, to a steering wheel including a heating element which may minimize a temperature deviation felt by a driver by heating an entire surface of a rim to a uniform temperature. The present invention also relates to a steering wheel including a heating element which may continuously generate heat even though a portion of the heating element is cracked or is electrically disconnected, minimize an increase in a diameter of the steering wheel although the heating element is employed, and directly transfer a transfer film, on which an aesthetic decoration pattern such as a wood pattern is printed, onto a surface of the heating element.
2. Background Art
A steering wheel is a driver-manipulated element of a steering system of a vehicle. Many studies have been conducted with regard to the steering wheel for improving its esthetic appearance, convenience of holding, use of functional elements therewith, etc. In particular, when starting to drive a vehicle in winter, a temperature of a steering wheel is lower than that of a human body, which affects the driver and might pose a safety-related problem. Accordingly, various apparatuses for heating a steering wheel to a temperature greater than that of a human body have been studied.
In a conventional technique for heating a steering wheel as disclosed in Korean Utility Model Application No. 1989-0020599, Korean Patent Application No. 1992-0000945, and Korean Utility Model Application No. 1996-16958, heating coils 3 are buried in a rim portion 10 of a steering wheel as shown in FIG. 1.
In order to bury the heating coils 3, as shown in FIG. 2, an insulating covering material 2 is coated around a core 1 and the heating coils 3 are bonded to an outer circumferential surface of the insulating covering material 2. Afterwards, a surface of the rim portion 10 is finished using a finishing member 4 such as a synthetic resin.
In another method of burying the heating coils 3, as disclosed in Korean Utility Model Registration Application No. 1996-066213 (FIG. 3), after winding a heating wire 5 in a coil shape on an outer circumferential surface of the core 1, a surface of the heating wire 5 is finished by using a synthetic resin mold 6.
However, as shown in FIG. 2, when the heating coils 3 are fixed around the outer circumferential surface of the insulating covering material 2, it is quite difficult to arrange the thin heating coils 3 at uniform intervals in a working process, and a temperature deviation between areas in the rim portion 10 occurs in practice due to irregular distances between the heating coils 3.
Also, as shown in FIG. 3, when the heating wire 5 is wound in a coil shape, a temperature deviation may also occur due to irregular winding gaps, and, in particular, since only one heating wire 5 is wound, when the heating wire 5 breaks during a working process, it is necessary to replace and re-wind the entire heating wire 5 again. Also, when the heating coils 3 or the heating wire 5 is buried as described above, it takes a certain period of time for heat to be transferred from the heating coils 3 or the heating wire 5 to a surface of the rim portion 10.
A plane heater 14 for a steering wheel is disclosed in Japanese Patent Laid-Open Application No. 2007-290685 (FIG. 4). In the plane heater 14, heating wires 17 are fixed to a supporter 16 formed of a nonwoven material. FIG. 5 is a photograph of an actual plane heater 14, and FIG. 6 is a photograph showing a steering wheel including the plane heater 14. As shown in FIG. 6, the plane heater 14 is mounted on an outer circumference of a rim of the steering wheel. The plane heater 14 provides a cushioning effect when a driver holds the steering wheel since the supporter 16 of the plane heater 14 is formed of a nonwoven material.
However, when the plane heater 14 is used, a thickness (diameter) of the steering wheel is increased due to the supporter 16 formed of a nonwoven material. Also, the steering wheel is finished by covering an actual wood 20 or a leather to protect the plane heater 14 and to gentrify a decoration. In this case, a thickness of the steering wheel is further increased.
The Cubic Printing (Curl-fit) method for a rim of a steering wheel of a vehicle disclosed in Korean Patent Registration No. 10-0472399 of the current inventor may not be applied to the plane heater 14 having a rough surface as described above. That is, a transfer film, on which a wood pattern for an esthetic decoration of the steering wheel is printed, may not be directly transferred onto the rough surface of the plane heater 14. For a decoration of the steering wheel, as shown in FIG. 6, after processing a wood piece 20, the processed wood piece 20 must be applied to the plane heater 14 (after processing two pieces of woods having a semi-circle shape, the two pieces of woods are joined to surround the surface of the plane heater 14).
In this case, the manufacture of the steering wheel is time-consuming, and thus, expensive. Also, due to the low thermal conductivity of the wood piece 20, the overall thermal conductivity of the steering wheel is reduced, and accordingly, heat of the plane heater 14 may not be efficiently utilized.